A significant portion of the construction industry builds residential and commercial structures. Contractors generally build structures in-situ at specific sites, and “manufactured builders” generally build sections of structures in a factory for assembly at a particular site. In either application, the structures are generally framed, roofed and then covered with exterior siding materials. One particularly advantageous and popular type of siding is fiber-cement siding. Fiber-cement siding products are typically made from a composition having cement, cellulosic materials and a binder. The fiber-cement composition is pressed, cured and then cut into panels, shakes and planks to form finished siding products that are ready to be installed on a structure. Fiber-cement siding products are insect resistant, fire resistant, and wear resistant. Fiber-cement siding products can also be painted like wood, but they are not made from a valuable natural resource. Therefore, many contractors and manufactured builders are switching to fiber-cement siding products from wood, composites, aluminum, plastic and bricks.
Several buildings also have soffits installed under the eaves where the roof overhangs the exterior walls. Soffits are conventionally made from wood, metal (aluminum) or plastics. Soffits typically have large holes that are covered with a large mesh screen or thin slots to provide ventilation and to prevent insects or birds from nesting within the structure. The large holes, for example, are generally 1.5-3.0 inch diameter circles or 2×12 inch rectangles that are cut with a jig saw or a cylindrical saw. Wood and wood composite soffits, however, have several drawbacks because they are subject to insect infestation, warping, rotting and fire. Aluminum and plastic soffits also have drawbacks because they are difficult to paint, and thus the color of the soffits may be substantially different than the color of the paint on the exterior siding. Therefore, because fiber-cement building products do not suffer from the same drawbacks as wood, plastic or aluminum building products, many contractors and manufactured builders would like to install soffits made from fiber-cement.
Manufacturing fiber-cement products, however, can be difficult because fiber-cement building products are more difficult to process than wood, plastics or aluminum. For example, cutting fiber-cement products with circular saws (e.g., a rotating abrasive disk) produces a significant amount of dust that makes the working environment unpleasant and difficult to clean. Fiber-cement building products are also relatively brittle and can easily crack during processing. Moreover, fiber-cement building products are much more abrasive than wood, plastics or aluminum, and thus they wear through cutting tools very quickly. Fiber-cement soffits are particularly difficult to manufacture because it is difficult and time-consuming to form apertures in fiber-cement panels that allow air to flow through the soffits. Thus, fiber-cement soffits are not yet widely used in the marketplace.
One particularly promising fiber-cement soffit is a 12-foot fiber-cement panel having a plurality of ⅛ inch diameter apertures in a uniform, symmetrical pattern. Manufacturers of fiber-cement building products, such as James Hardy Building Products of Fontana, Calif., have experimented with manufacturing such fiber-cement soffits by drilling the apertures. Drilling the fiber-cement panel, however, is not generally feasible in large scale production because it is too time-consuming and the abrasive fiber-cement quickly wears down the drill bits. Drilling the fiber-cement panel also produces a fine dust that is unpleasant and difficult to clean. Therefore, drilling the apertures in the fiber-cement panel is not a viable manufacturing process.
To overcome the problems of drilling fiber-cement panels, manufacturers of fiber-cement building products have also experimented with punching individual holes through a fiber-cement panel using a sheet metal punch. Typical sheet metal punches have a very small clearance between the punch and the die. Punching apertures through the fiber-cement panel with a sheet metal punch is also not feasible because the sheet punch metal often sticks to the fiber-cement panel. The sheet metal punch may thus delaminate portions of the panel as it withdraws from the aperture. Punching apertures through the fiber-cement panel with a sheet metal punch may also produce a mushroom-shaped plug such that each aperture has a small opening on the front side but a much larger opening on the back side. In preliminary tests using a sheet metal punch to form apertures in a fiber-cement panel, the sheet metal punch ripped out so much material from the backside of the panel that a typical 12-foot soffit may not have sufficient structural integrity to be hung under the eaves of a structure.